linux 下使用poppler qt5

poppler qt5是poppler的扩展模块，使用qt图形库的开发者对于开发pdf插件来说，这个开源库无疑是非常方便的。本篇介绍如何使用这个库，并且配置开发环境。

1.在poppler官网下载源码，解压到本地目录后切换到这个根目录，打开命令行：

• $./configure

• $make

• $sudo make install

2.编译安装完后，我们用命令行查一下包，并且安装对应的开发库：

• $apt-cache search poppler-qt5
  

• $sudo apt-get install libpoppler-qt5-dev
  3.安装完了我们就可以子qt中使用这个库了，如果不确定有没这个包，可以通过一下命令检查一下：

• $pkg-config --cflags poppler-qt5

4.在qt 的工程文件中添加一下配置

这时候就能使用poppler qt5的库了，它提供了很方便的接口。写一个例子获取pdf文件的第一张截图：

QPixmap FilePreviewIconProvider::getPlainTextPreviewIcon(QString fileUrl){
    QFile file(fileUrl);
    if(!file.exists())
        return QPixmap(QSize(PIXMAP_WIDTH,PIXMAP_HEIGHT));

    if(!file.open(QIODevice::ReadOnly))
        return QPixmap(QSize(PIXMAP_WIDTH,PIXMAP_HEIGHT));

    file.waitForBytesWritten(200);
    QString text = file.readAll();
    file.close();

    QStringList strs = text.split("\n");

    QImage img(QSize(PIXMAP_WIDTH,PIXMAP_HEIGHT),QImage::Format_ARGB32);
    QPainter painter(&img);
    QFont font;
    font.setPixelSize(12);
    painter.setFont(font);
    QPen pen;
    pen.setColor(QColor(0,0,0));
    painter.setPen(pen);

    int counter = 0;
    for(auto line : strs){
        QString str;
        QStringList subStrs;
        for(int i = 0;i<line.length();i++){
            if(QFontMetrics(font).width(str)<(PIXMAP_WIDTH-15))
                str += line[i];
            else{
                subStrs<<str;
                str ="";
            }
        }

        for(auto subline:subStrs){
            painter.drawText(5,12+counter*15,subline);
            counter ++;
        }

        painter.drawText(5,12+counter*15,str);
        counter ++;
    }

    return QPixmap::fromImage(img);
}
QPixmap FilePreviewIconProvider::getPDFPreviewIcon(QString fileUrl){
    Poppler::Document* document = Poppler::Document::load(fileUrl);
    if((!document || document->isLocked())){
        delete document;
        qDebug()<<"file reading error....";
        return QPixmap(QSize(PIXMAP_WIDTH,PIXMAP_HEIGHT));
    }
    qDebug()<<"pdf document read successfully!";

    if(document == 0){
        qDebug()<<"pdf page is null";
        return QPixmap(QSize(PIXMAP_WIDTH,PIXMAP_HEIGHT));
    }

    Poppler::Page* pdfPage = document->page(0); //Document start at page 0

    QImage img = pdfPage->renderToImage(72,72,0,0,pdfPage->pageSize().width(),pdfPage->pageSize().height());
    if(img.isNull()){
        qDebug()<<"render error";
        return QPixmap(QSize(PIXMAP_WIDTH,PIXMAP_HEIGHT));
    }

    img = img.scaled(QSize(PIXMAP_WIDTH,PIXMAP_HEIGHT),Qt::KeepAspectRatio,Qt::SmoothTransformation);
    delete pdfPage;
    return QPixmap::fromImage(img);

}